DESCRIPTION: This laboratory has been a leader in research on the function of non-conventional myosins in yeast. They made the remarkable and still curious discovery that overexpression of a kinesin, Smy1, could suppress the loss of function of a non-conventional myosin (Myo2 of the dilute or myosin V family). Their subsequent analysis also shows that the kinesin and myosin co-localize at the tip of the bud and they depend on actin but not microtubules for their localization. Also, extensive attempts to demonstrate that the kinesin either depends on or interacts with microtubules have been negative. The kinesin also has not shown microtubule motor activity in vitro. Therefore, the function of this kinesin may not be as a microtubule motor. This laboratory has also found interaction between this kinesin and the conventional myosin, Myo1, which is unexpected. The revised aims are directed at elucidating the function of these myosins and kinesins in vivo and how they interact. Aim 1 is to identify and characterize proteins that interact with the kinesin, using a two-hybrid screen and immunoprecipitation. Aim 2 is to identify genes that interact with Smy1, using a synthetic lethal screen. Preliminary results already identify some interesting genes that interact, including another myosin, Myo1. Aim 3 is to look specifically for interactions of Smy1 with other myosins, MYO3, 4 and 5, because interactions with MYO1 and 2 are known. The interaction with Myo1 will be characterized more thoroughly, examining features that are seen in the interaction with Myo2. Aim 4 is to determine whether Smy1 is a microtubule motor. Substantial preliminary work indicates that it is not, but the conclusion is so remarkable that additional experiments are proposed.